Gas expanded rubber



Patented Nov. 18, 1941 i UNITED STATE GAs EXPANDED n nnnn'- Dudley. Roberts, New York, N. Y., mm. to Rubatex Producta-Ina, New York, N; Y., a cor poration oi. Delaware No Drawing. Application December 20, 193:; Serial No. 246.80: v 1

2 m (01. etc-r24) QMyHinVentiQn" relates to a novel gas expanded product and a novel process of manufacturing the same and more particularly relates to a'novel expanded rubber and process for gassing the rubber to eliminate undesirable'odors,'fl'ame-proof the product and increase the sound and heat insulating properties thereof.

In application Serial No. 718,875, illed April 3, 1934, now Patent No. 2,067,0 0, issued Jan a y 5, 1937, of which this application is a continuation in part, I have'disclosed a novel expanded rubber and process for manufacturing the same. This application is a continuation inpart of application Serial No. 755;464,filedNovember 30, 1934. n

Briefly, the process of my present invention involvesnew methods for gassingrubber to make gas expanded cellular rubber includingboth closed cell and open cell rubber. 'The novel gassing process includes the use of mixtures of gases including nitrogen andammonia, sulphur dioxide and chlo rine. I further contemplate the use of ammonia; sulphur'dioxide, chlorine and C water vapor gases per se, either for the original gassing of the rubber'or for subsequent gas treatment of the rubber to' eliminate the odor of the hydrogen sulphide contained v within the cells of the mass. Theselatter gases react with the hydrogen sulphide to produce sulphur 'compounds with non-objectionable odor.

In the formation of" closed cell rubber I propose partiallyvulcanizing the'rubber in the first stage prior to or during the gassing step to give the rubber sufllcient strength to maintain its desired closed cell structure; r Y

In the formation of open'celled orsponge rubber I prevent such partial; vulcanization ofthe rubber as would cause it to hold the gas within it in the form of closed cells and eflect a gassing operation in such away as to cause ruptured cells and intercommunicating channels through the rubbermass. I

Many methods or making open'celled sponge rubber have been'suggestedin the prior art but I have found them deficient from the standpoint of excess 0! weight because of the chemical blow-- ing agent contained therein, or undesirable from the standpoint oi lack of optimum expansion because of insuflicient 'gassing'br because of a premature set or cure of the 'rubber' beforeit reaches the optimum point of expansion. The problem of therespective solubility oithe difierent gases in the rubber and their 'r'elationto'the open celled or closed cell form of rubber desired are also taken up in the present application;

In the formation of closed can rubber of'r'the soft or'resilient type it "is important that the gas employed as a gassing agent or at least-a, part or that gas berelatively insoluble ,in therubber so that it remains within the cells of the rubber. If the gas is one that is relatively soluble in the rubberandtherefore diffuses outward from the-rubber, it would cause collapseoi the cellular structure because 0! the subatmospheric pressure within the cells. When'hard closed cell" rubber is made using a-high'amount ofsulphur then this problem does not arise because of the. rigidity of the rubber itselfwhich has sumcient' strength so that it' is self-supportingwith or without the gas contained vwithinits cells.

When open celledor sponge rubber is made then since there is free' communication between the outside and inside of the rubber structure the gases are always free to pass. in or out and" the-solubilityof the gases is'unimportant except with respect to its penetrationjinto thei rub-v ber to form the internal gassed cellular structure. Y f

The closed cell gas expanded rubberf'which I produce according to the present process is characterized by a high degree of expansion "and theretorean extremely light weight. The .hard closed cell material may weigh as little asabout three pounds per cubic foot. Soft material may weigh as 'little'as'flve orsix poundsf'percubic foot. These materials are characterized by impermeability to water, high degree of,insulation strength. 7 1 I In the manufacture of closed cell rubber in accordance with my invention I, contemplate inwith 'respect to heat and electricity and good troducing for example agas such as ammonia 7 mixed with nitrogen gas; theammonia or the nitrogen may 1 either be v introduced simultane ouslyor successively. When introducing-them successively, I prefer to employ first the nitrogen and then the-ammonia. since the ammonia has an action to eilect the acceleration of thevuldeveloped within the rubber to convert the hy drogen sulphide and therefore to eliminate the objectionable, odor. 1. i i, t.

.I-Iowever. the 118870! azmixture ofammonia gas with nitrogen has other important advantages over-the use otnitrogen gas per se. As

will be brought out more specifically hereinaiter property and,

' the rubber mix at the desired point.

. v ,7 f1 Data from I spongewithinit."

Both closed cell rubber andopen celledrubber may be-made according to the processes I shall set forth. In the manufacture of closed cell rubher I preier toemploy a mixture of nitrogen and f set forth :this" mixture may be injected into the Y rubber in an autoclave or itmay be generated I I included within the rubber. I Similarly, I can employ mixtures of. nitrogen end :7

sulphur dioxide. 1 have from chemicals "chlorine or nitrogen and example; nitrogen.

cape'oi. the g not cause collapse of,-the ;mass.; ,The relative y rubben solubilitiesqof the. various gases with: n: 'is. set forth.in the;tables;below. 5,1 (i "Daynes on the-relative solubility u U WW l lyih' g '.-L-',-"'.Y

Carbon 1monoxide' Nitrogen at; dibeiqej s w i wsfimem j I .1.o.f 1

Nitrogen. Ammonia;

ess; I include such' as carbon dioxide:

include within the mix retarders of. acceleration, such as aldehydes. I :then subject. the rubber insufficient to effect such a vulcanization of the I rubber as'willcause'itto'set. ms' retardation After the rubbernes. iv ed blow-it:is

' subjected toiextern u tappneq as sum. as amzv also found that I can get-good results bygassing; with-chlorine alone, inwhiclievnt-the chlorine- "bothexpands the rubber and forms cells of as therein,; and at the same. time chemicallyv acts with the rubber to convert it "to rubber chloride, v I mayalso employ ammonia gas alone as the I I gassing agent. 7' j j I 1When Imake' 1closed-cellJ rubber of the; soft; 1varietyyit.isessentialthat I includeas at least one' of the gassingagents a gas thai'l-is-relatively insolublein the rubber,such a gas being; as for? If. a relatively soluble gas be} I used aloneias the gassing. agent, thenit tends to diffuse out from therubber; and;,collapse ofl; thesoft structure occursA-i'when I make closed; cellhardrubben-then I may employ af gas thatj issolublefin the rubber, such'as carbon dioxide or ammonia; inasmuch 2 as. the ,--r ubbei' itself sufficient strength, because of .its, high;sulphuri content, to form a rigid structure, and the es- 5 from th cells asby. diflusion does;

I'also; propose themanufacture of.o1: en-celled rubber accordingto the followingbproc within the; rubber a' *chemical' agent adapted 'to 2 decompose ,and evolve a:.gas and-I may or may not' i monia or nitrogen which acts to further expand it uponits' release from such gaspressure. Heat;

is-applied which causes expansion of the gas con the rubber to getthe optimum exammonia gases ;to' the rubber gas. .ss;has1eeen.;.;

' the neighborhood of orf. bove-,300f F.

tained within panslolr and theheat also completes the vulcanization to cure the rubber.

in th curing" of the-rubber;;to1;get the; quick set at'itshighestpoint of eitpansion; .if When I emaldehyde type such as'acetaldehyde,'paraformaldehydeand furfuraldehyde, I premature vulcanization of thefrubber I preier-tO. -use ammonia gas\as' v the subsequently applied gas since the ammonia 7 acts -;to convert the aldehyde to analdehyde' amine which'actsas' an accelerator to the vul-I caniz ation and induces a. quick set for the sponge- I ,tat,.the,point'of optimum, expansion; .There. is 4 an added blow induced "bothin' .the'closed cellrubber-and in the open celled or sponge rubber because; of the, presenceyO h drogen; sulphide 1 gas' which is developed 'in an"exothermicreac5 -i ploy retarders of the and the like, to prevent tion-in thefrubber w en the. temperature, is

This

drogen sulphide f gas which is developed causes "agoodvolumetricblow inftherubber andfurthei i obnoxious odors of the mass f .odor of the hydrogen sulphide" is responsible for I 'I'ogliminatethe M as formed l have proposedjtheuse' of ammonia gas as set forth aboverijIjhe ammonia reacts with i I the. il msensm deandt m a o i m ulphide which non ob'jectionable in smell and u mix-,to'fsufilcientheat:lto decompose the blowing I agent and cause evolution ot gas; the" heat being act with the hydrogen and. the sulphur dioxide 'mayiibe;

,Another gas that is valuable I further propose the use of chlorine gas tore+ smell :by,conversion of the hydrogen sulphide:

' The chlorine can be externally injected into-tithe v rubber 'or it can bedeveloped by the inclusion within the rubber mass;v of chemicals adapted; to

react to produce chlorine gas. i.As has been stated bination with Alternatively, I, may employ 'sul'phur dioxide in" way to. react Iwith" the. hydrogen sulphide lectedinto the pb'er. sagas ;1,. ,1

, v ss i yro me manufacture of sponge'or open vlcellecl rubberisj water vapor gas; Because of its;liigh' solubility rinithe rubber itcannot very {well be used in closed f cellrubber since .it -wouldjtend to diffuse out very rapidly. Howeverflfit can betemployed in the manufacture of sponge and thefmethod I suggestis to effect ap'rel'iminary blow of rubber tirith a blowingagent adaptedtd release jagasas for W carbon dioxide} and follow this [gassing l 0r qn i .trs mnflz plating t b1w11 "155$ xam in jtmosphere of .water vapor v such' as 'st'eam und r rfi a ly l W lp es it r exa p eit fi l to 100' poundslper square inch, whereuponi'the. T

waterwaporgas penetrates the rubber and upon subsequent "heating jor release; of pressure causes ber because therubber does not haveisumcient' strength' to' prevent-the ruptureof Ithe gas cells a large volumetric es'pa nsion. .Vulcani'zation l at the-end po tsets upjil eexpanq dspo ge um Q ber,

the formationoffsponge I propose is especiallyadvantageous since the second stage. e'zgt'ernal; gassing-not only acts to expand. the "alreadyaformed gas cells within the ubbe ith cel s wnlchj av beeaset u y the. chemical blowing agent) but the externallyapj r a -8 s... n rat through these established 8 S;;9 1Q1i nd m resnate'sthe rubber When I employ ammoni'a as this gassing agent, the ammonia assists 7 sulphide to eliminate its a externally in- I mogenously and extensively throughout. By res I This is important because one of theprimary 7 problems in obtaining the best possible sponge rubber is to obtainthe maximum volumetric expansion since a greater volumetric expansion means less rubber" present ;'per unit volume and lighter weight. As has been stated'because the o present combined blow process comprises first setting oil the chemical blowing agent-within the rubber to form gas cells and open-channels through the, rubber to enable the gas externally applied in thesecond stage to more'eilectively penetratethe rubber completely throughout its mass, it makes foran entirely new and superior 5 sponge rubber of extreme'lightness;

It is, therefore, the object of my invention to provide a novel method of gassing rubber using a mixture comprising nitrogenand ammonia, ni-

trogen and chlorine, and nitrogen and sulphur dioxide.

It is another object of my invention to provide a novel process of gassing rubber using ammonia, chlorine or water vapor gas per se. v

Itis a further object of my invention to treat cellular rubber whose cells contain hydrogen sulphide gas with chlorine, ammonia or any gas that will react with the hydrogen sulphide to form unobjectionable sulphur compounds.

It is still another object of my invention to make a cellular sponge rubber by incorporating within the rubber a chemical blowing agent, setting oil the chemical blowing agent to form open channels within the rubber, and then gassing with an externally applied gas to provide a further expansion for the sponge mass.

It is still a further object of my invention to gas rubber with a'gas that produces a flame proofing salt within the rubber.

As I have stated the gases which I employ may be externally injected into the rubber'or they may be evolved by the decomposition or reaction of chemicals included within the rubber. Such chemicals and salts which decompose under heat or react to evolve these gases are well known to those skilled in the art. Nitrogen, for example. may be evolved from diazoaminobenzene or from the reaction of sodium nitrite and ammonium chloride. Ammonia maybe evolved from ammonium salts such as ammonium carbonate and amino compounds. Chlorine may be evolved from certain unstable chlorine compounds such as the chlorates or from liquids containing'con centrated chlorine such as the hydrochlorides. I

The. rubber mix is prepared by millingwithin rubber suitable quantities of sulphur and accelerator and blowing agent, when such is employed, in substantially the following proportions: 1

r The above ingredients are thoroughly mixed with the rubber on the mill and the rubber mix is then heated to decompose the-blowing a nt, .which evolvenitrogen ammonia gases to ef-.

feet the results set forth'above.

When it'is desired'tomake the novel spongeby the combined blow process I have set'forth, Iuse j heffollowing mir; 1

Rubber Sulphur Carbon dioxide blowing agent.

The ingredients are thoroughly incorporated in the mix and it is essential that the accelerator be one that does not eflect the vulcanization of the rubber at the temperatures atwhi'ch the chemical blowing agent is'set oil.

;The rubber'mix is then subjected suillcient heat to;; dec0mp0se the,blowing agent and cause evolution of carbon dioxidefgas which forms open cells or;, channels throughout' the mass without stiflening the rubber. The sponge rubber is then subjected to ammonia gas under relatively low pressure, asrfor example 1 0 to 100 pounds per sq. ft. and the ammonia penetrates the rubber throughout, especially because of the communia cating channels already formedinthe rubber mass. On release of the gas pressure and subsequent heating, the ammoniagas in the rubber causes greatly increased expansion "not only in the cells formed by the blowing agent but also in the rubber ungassed by thedecomposed chemical blowing agent. The heat applied effects the vulcanization and set of the rubber and this set is hastened by .the action of the ammonia gas which permeates through the mass of the rubber. It is desirablethat a quick set be obtained afteragent and evolve nitrogen and ammonia therefrom, while at the sam time effecting a partial cure for vulcanization of the rubber so as to setup the rubber suiliciently so that the evolved gas is maintained within the rubber in the form of closed cells. If the rubber is not properly set up to give it 'suilicient strength, the cells are ruptured and a sponge is formed.

f llhe mixture of nitrogen and ammonia has new and useful results. First. itacts as a good volumetric expanding agent. Second, the

has an afllnity for the free sulphur presnt'and also the hydrogen sulphide gas with which it reacts to form" ammonium sulphlde,-

which not the objectionable odor of hydro- I en sulphide.

Therefore, this interior does not have the strength necessary to maintain the desired closed cell structure and a sponge or brokencelled in-'- terior often results. When the ammonia gas is set off uniformly throughout the rubber'in admixture with the evolved nitrogen gas,it has a Accelerator-cap l (nie rcaptobehzothiozole) .2 1

I, certain curing actionon;-;the rubber togive it this desirable feature of'homogeneous cure.v

Inthe-manufactureiof closed jcell gas expanded rubber the use=of algasgthat reacts withltherubher to convert, ,thexrubbentq a; derivative thereof i has special advantages. I have proposed ga sing V I the. rubber with chlorine'gasi Chlorine readily enters the rubbernwhen used alone or in com-.-

I bination withanother, gas such as nitrogen, It;

- effects thesdesired expansionv of the rubber material being 'expan dcd fi th f has. been present in the rubber a short time it reacts therewith ,un'der; form a rubber chloride fThrubber chloride is the form of a cellular mass.-:

'forrn edjfirst" in v thefdormjqf 'fihns that coincide with the cell Walls; This tends to prevent the; outward diffusion of the gas from'the blallsan'd in the case or the' fo rmation of a soft'and flexible thusip ropo'se to" usjelanfihfiatin'g gas that reacts with the rubber peinggjasj edjto; form both a Icelrubberderiva'tive;

miar structure and at t e s me time modified This principlefis iartibularly efiectivein the formation of jeXD'andedplastics and resins since Infthat case I canfefiectthe finalhardenini 6r setting of the plastic while atthesametime effecting its expansion by'th use of a gas that reacts with or accelerates:theconversionof the l0 11. In themanuf acture of open celledvgas' exfavorable cizirniitions to The vanous' gases and e the rigidity or softi'iessrequired. I intend' toi be limited. not by? the particular j statements herein 7 My, invention s ;i'lOt confined to the manufac-fy ture, ofje'xpanded rubber butfmiay be use with"; v

plastlcs o'r resinjs generally,

k v 'ombiriations of gases: Lhav e' set forth" arejmade by wayfor exampleg- The ;rubber composition" mayfvary according" to but y e h p nded ims; J

Icla'imf panded. rubber, theQste'ps 'of incorporating a 'clien'riical blowing agenti within the rubber:heatj A m me rubber to evolve "g'as'from the chemical blowing agent, .thus forming opence lls and chan- =ne1s throughout the rubbe'nygassing the rubber:-

with. an externally appliedigas; expanding the v------1' ul:)be,r andl v lcaniizingthe' open celled-rubbe closed cell rubber this'isflaninibortantfactort -I 2.' -Ir'1 thejmanufacture, of open celled gas 89! v panded rubber,;,. the stepsjoi 'ine orporatingja' chmibalblovvin agentwithin the rubber; heat ing the ifubbei'to evolve gas from thevch'emic'ali blowing agent, thus forming open cells and chanj-- n'els' throughout the] rubber; gassingfi the rubber with ;externallyv applied ammonia expanding the rubberf and vulcanizing'the open celled rubberg oBER rsQ 

